Crude oil contains a sizeable number of fractions, with asphaltenes and resins being among the heaviest. These two fractions are believed to be largely responsible for most of the problems encountered in the production, transportation, refining, and processing of crude oils. Most commercially valuable petroleum refinery products (e.g., naphtha, mineral oil, gasoline, kerosine, turbine oil, gas oil, diesel oil, lubricating oils, and paraffin waxes) are typically obtained after the removal of asphaltenes and resins from the crude oil.
It is highly desirable for the crude oil producer to remove asphaltenes and resins from the crude oil prior to transporting it to a refinery through pipelines. Pipeline transportation of these heavy crude oils is typically extremely difficult primarily due to the tendency of these materials to emulsify with water. The heavy crude oils are also undesirably highly viscous. Transporting these heavy crudes often requires adding a diluent and/or heating the pipeline. This is undesirable in that it can be very expensive, hazardous, and can result in emission and crude oil light fraction losses. Prolonged use of a particular pipeline to transport heavy crude oils may cause asphaltene deposition which can decrease the throughput of the pipeline and its efficiency.
It is conventionally believed that asphaltenes and resins stabilize water-in-oil crude oil emulsions. Subsequent removal of the asphaltenes and the resins from the crude oil can facilitate breaking the emulsions prior to the transportation of the crude oil. This is advantageous in that it is capable of reducing the cost of transporting wet crude oils and is capable of minimizing or eliminating pipeline corrosion caused by water and salts dissolved in the aqueous phase of the crude oil. Another significant potential advantage associated with the removal of asphaltenes and resins from the crude oil is the consequent reduction in transition metals (e.g., vanadium, nickel, and iron) which are capable of poisoning catalysts used in refineries. Finally, removal of asphaltenes and resins from the crude oil is significant in that it may help mitigate problems relating to the presence of SOx and NOx gases in the effluent.
Atmospheric and vacuum distillation has been used as well as clay and sulfuric acid treatment methods in asphaltene and resin removal. Several drawbacks are associated with distillation technology such as high energy consumption, cocking, and the difficulty of removing sulfur and nitrogen from the distillates. Propane deasphalting is a current popular conventional technique used in petroleum refineries. Notwithstanding any advantages, propane deasphalting may be undesirable in that the crude oil should be first dewatered and transported to the refinery before the deasphalting process can be employed. Additionally, propane is highly flammable. Moreover, the separation of propane from both the deasphalted and the residual fractions typically requires the system to be heated which results in additional energy consumption.
There is a need in the art for a deasphalting and deresinating process which addresses the problems set forth above.